Cement.



and repeated failures have resulted.

of pure gypsum rock.

UNITED STATES PATEN FF 10F THOMAS JONES, OF ACME, TEXAS, ASSIG-NOR TOACME CEMENT PLASTER COMPANY, A

CORPORATION OF ILLINOIS.

CEMENT.

To all whom it may concern:

Be it known that I, THOMAS JONES, a citizen of the United States, and aresident of Acme, in the county of l-Iardeman and State of Texas, haveinvented a new and Improved Cement, of which the following is a full,clear, and exact description.

My invention relates to cements, my more particular object being toproduce a type of cement analogous to the well-known article of commerceordinarily designated as Keenes cement.

The so-called Keenes cement, generally speaking, is a gypseous plasterwell known and extensively used in England (where it originated), andalso upon the continent of Europe. It is employed in instances where ahigh degree of finish combined with extreme hardness and strength arerequired for plaster work. The original method of its manufactureconsisted in steeping dehydrated gypsum in alum solution and thenrecalcining. The process, however, was quite expensive. Numerous futileattempts have been made in the United States to manufacture this cementor its equivalent They are due, no doubt, to imperfect acquaintance withthe nature and chemical properties of the essential materials, and withthe roper method of treatment of these materia s. It is probable thatmanyfallacious statements as to the method of manufacture of thiscement, which have been given publicity in various technicalpublications, are mainly responsible for ignorance of the essentialrequisites for the production of the cement.

, The object of my present invention is to produce a material of thegeneral nature of so-called Keenes cement, my product being a materialof the highest grade and excellenee and made by the most direct methodand at the least possible expense. I employ only one calcination. Theplasticity and ultimate hardness of the product are brought about bychemical substances added together as hereinafter described.

The first step in my method is the selection This must be practicallyfree rom magnesia and iron. If magnesia be resent in the rock it causesthe formation 0 magnesium sulfate, which is detri- Specification ofLetters Patent.

Application filed April 29, 1908.

Patented March 23, 1909.

Serial No. 429,889.

mental, and the presence of iron even in very minute quantities causesthe formation of iron salts which weaken the finished cement and alsodiscolor the same. Pure gypsum rock having been found in a suitablequantity I break the rock into pieces of convenient size, preferablyeach of about twenty pounds weight, and place in a suitable kiln, at thesame time scattering over the charge, so as to be evenly dispersedthrough the mass, forty pounds of tribasic aluminum sulfate (Al O bO 3IlO) in the form of a fine granulated powder, for every one thousandpounds of gypsum rock, and then calcine until the charge is of a fullred heat. The calcination may be effected either in contact with thegases of combustion or out of contact therewith, the main requisitebeing that the material be subjected continuously to a perfectlyoxidizing atmosphere. This may be accomplished by the admission of anamount of air to the fire-box or flue suflicient to oxidize completelythe fuel gases before their entrance into the kiln or oven. WVhen thecharge has been perfectly calcined and is afterward cooled, I transferit to a crusher and then to a mill in which it is reduced to a finepowder. This powder (consisting of anhydrous sulfate of lime andanhydrous subsulfate of alumina) is laid aside for the mo ment I nowtake of caustic potash two hundred and twenty-four (224) pounds, which Idissolve in twenty (20) gallons of water in an iron an which I heat frombeneath. The solution is thus caused to boil, and while boiling hot Iadd to the solution three hundred and sixty (360) pounds of a pure andfinely comminuted silicious sand. Under suitable conditions, however, asmaller proportion of the sand will suffice, various proportions thereofbeing employed according to purity of the materials. I keep the solutionboiling and constantly agitated until all of the water has been drivenoff; there remains a viscous mass of potassium bisilicate which rapidlysets and hardens. I allow the mass to cool, and then break it intofragments of convenient size. These I place in a suitable oven orreverberatory furnace and burn them at a full red heat (substai'itiallyas above described with reference to the gypsum rock) for a period ofeight or ten hours until incipient vitrification ensues. Then, while themass is red hot and in a viscous condition, I withdraw it from thefurnace and plunge it suddenly into two or three times its own weight ofwater. This water should be held in a lead-lined tank provided with awater jacket and with means whereby the tank may be heated. Violentebullition ensues and the heated mass becomes dissolved in a fewminutes. If the solution were effected by other means it might requireseveral hours in its accomplishment.

lVhen the solution of the heated mass is complete, I allow it to cool,and then pour it by degrees into a solution consisting of one part ofordinary commercial sulfuric acid and two and one-half parts of water byweight and thoroughly mix the two solutions together. The silicate mustbe added to the solution in such proportion as to neutralize perfectlythe acid in the water, the product consisting of a stiff paste ofpotassium sulfate and gelatinous silica. I then transfer this paste todrying ovens in which I allow it to remain until all uncombined water isexpelled, taking care to avoid too high a temerature in so doing, asthis would occasion ecomposition of the sulfate. I therefore never allowthe heat to approach that of redness. It it now removed and thereafterground to a fine powder, either by itself or admixed with the burnedgypsum and alumina. If the materials are ground together care should betaken to maintain them in proper proportions. These are from twenty totwenty-five pounds of the compound just described, to one thousand andfifty pounds of the burned gypsum and alumina. Being admixed in thisproportion the process is complete. The product then consistsapproximately of the following ingredients:

Calcined gypsum 1020 pounds. Sub-sulfate of alumina 30 Dry gelatinoussilica 14 Potassium sulfate- 11 The product just described is a cement.

For the decomposition of the potassium bisilicate I may use eitherpotash alum or normal aluminum sulfate (111 0 350 admixed with eighteenparts of water. This gives excellent results when proper proportions aremaintained as above described, these being substantially the proportionsin which the several chemical re-actions take place.

The silicate compound above described consists of dry gelatinous silicaninety-one parts, and potassium sulfates eighty-seven parts. When thiscompound is ground separately from the gypsum, the mixture of gelatinoussilica and potassium sulfate should be twenty to twenty-five parts toone thousand and fifty parts of gypsum and alumina. These proportionsare based upon the balanced affinities of the several elements for eachother and can not be departed from to any great extent without injury tothe product.

By the calcination of the gypsum rock in contact with the tribasicaluminum sulfate, I greatly reduce the cost of both calcination andgrinding, thus dispensing with unneceslabor and cutting down the cost offuel.

Not only this, but the quality of the burned gypsum is greatly improved,while the tribasic aluminum sulfate is itself erfectly calcined. This isa result most di 'cult to accomplish by itself, for the reason that whenheated, the tribasic aluminum-sulfate runs together in a mass whichrenders its calcination unequal, thus necessitating the waste of muchfuel and requiring much time and patience to effect a thoroughcalcination. Much time is also gained and the effectiveness of materialgreatly increased, by the withdrawal of the heated bisilicate andplunging the latter suddenly into the water. I find that by this stepthe solution of the bisilicate is quickened to such an extent that it isas complete within a few minutes as would otherwise be the case in asmany hours.

The perfect decomposition attained by treatment of the bisilicate withacid, resulting in the formation of gelatinous silica and potassiumsulfate, produces a material which may be ground with as much ease asthe gypsum itself. Moreover, this brings the ingredients into exactlythe condition required for combination with the gypsum in the ultimateproduct.

By the method of treatment above described, I find that there is anotheradvantage, to wit, I can subject the compound to a comparatively highdegree of heat and thereby secure a more complete combination betweenthe silica and the alkali, and effect a more thorough decomposition thanis possible by grinding together the two compounds.

By withdrawing the mass while in a viscous condition an opportunity isafforded to re-charge the furnace and allow the calcination to proceedcontinuously. When potash alum is used to decompose the silicate, onehundred and fifty-eight pounds are allowed for every fifty-six pounds ofcaustic potash used. If normal aluminum sulfate ato sso 1811 0) be usedfor the purpose, one hundred and eleven pounds for every fifty-sixpounds of potash will be required to effect the same approximate result.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

1. The cement herein described, containing calcined gypsum, sub-sulfateof alumina, dry gelatinous silica, and potassium sulfate.

2. The cement herein described, containing the following substances inthe proportions stated, to wit: calcined gypsum one thousand and twentypounds, sub-sulfate of alumina thirty pounds, dry gelatinous silicafourteen pounds, and potassium sulfate eleven pounds.

3. The method herein described of preparing a cement, which consists inadding tribasic aluminum sulfate to gypsum rock, calcining the admixtureto a red heat, crushing the residuum to powder, preparing potassiumbisilicate, subjecting said potassium silicate to the action of sulfuricacid so as to form potassium sulfate, reducing said potassium sulfate tothe form of a dry powder and admixing said potassium sulfate with saidfirst-mentioned powder.

4. The method herein described of preparing cement which consists incalcining gypsum rock and tribasic aluminum sulfate, re-

ducing said materials to the form of a powder, preparing potassiumsulfate also in the form of a powder, and admixing said powderstogether.

5. The method herein described of preparing cement, which consists inmaking potassium bisilicate at a red heat, bringing it suddenly intocontact with water, so as to cause it to form a solution therewith, andadmixing it with sulfuric acid so as to form potassium sulfate.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

THOAIIAS JONES.

\Vitnesses:

J. L. ELBERT, S. J. MATTHEW.

